The present invention relates to relocation of communication services in a communication system and in particular, but not exclusively, to relocation of one or more communication services from a network element of a cellular communication system, the element being arranged to provide control of at least two different communication services provided for a mobile station.
Communication networks typically operate in accordance with a given standard which sets out what the various elements of the network are permitted to do and how that should be achieved. The given standard also defines the types of connections by means of which the communication service is provided for a subscriber of the communication network. For example, the standard defines whether the subscriber or more precisely, a subscriber terminal is provided with a circuit switched service or a packet switched service for communication, and also the manner how the circuit switched or the packet switched service is to be implemented. Thus the various standards define several different xe2x80x9crulesxe2x80x9d for communication. The rules are often referred to as protocols. The protocols may be used for controlling various events and functionalities in a connection provided through the communications network. Several protocols may be simultaneously in an active state for providing control of a connection.
A subscriber terminal that is to be used for communication over the given communication network has to be implemented in accordance with the standard. A subscriber terminal may also be arranged to be compatible with more than one standard, i.e. the terminal may use several different types of services for communication. It is also possible to have several communication connections based on different standards at the same time. For example, a terminal may simultaneously communicate in parallel through a circuit switched (CS) connection and a packet switched (PS) connection.
A communication network is a cellular radio network consisting of cells. In most cases the cell can be defined as a certain area covered by one or several base transceiver stations (BTS) serving mobile stations (MS) or similar user equipment (UE) via a radio interface and possibly connected to a base station subsystem (BSS). Several cells cover a larger area, and form typically a radio coverage area referred to as a location area (LA) or in some standards as a routing area (RA). It is noted that the size of the location area or routing area depends on the system and circumstances, and may equal to one cell or be even smaller, such a part of a coverage area of a base station.
A feature of the cellular system is that it provides mobility for the mobile stations, i.e. the mobile stations are enabled to move from a cell or location area to another, and even from a network to another network that is compatible with the standard the given mobile station is adapted to. Mobile stations having an active i.e. ongoing connection may also be relocated from the network apparatus of one location area to network apparatus of a new location area during an ongoing connection. This is enabled by a location management functionality that keeps record of the current locations of the mobile stations, and controls and proceeds the relocation of any ongoing connections between the mobile station and the network apparatus.
A mobile station (MS) within a location area of a communications system may be controlled and a location management functionality may be provided by a controller node. A cellular communications system also typically comprises a location register or several location registers for the location management purposes. The location area may be referred to as a servicing area of the given controller node. The location management functionality operates typically such that whenever a mobile station enters a new location or routing area, the control of the connection is xe2x80x9crelocatedxe2x80x9d from the xe2x80x9coldxe2x80x9d control node servicing the xe2x80x9coldxe2x80x9d location area to a xe2x80x9cnewxe2x80x9d control node servicing the new location area, and all control in the xe2x80x9coldxe2x80x9d node is cancelled.
For example, in a circuit switched GSM (Global System for Mobile) network the controller functionality is provided by means of a mobile switching center (MSC) and the location information of a mobile station is maintained by appropriate home location registers (HLR) and visitor location registers (VLR). In a general packet radio service (GPRS), that is an example of a packet switched cellular radio network, the service area of a GPRS may be controlled by means of a serving GPRS support node (SGSN). The SGSN corresponds substantially to the MSC of the GSM, but is implemented to provide packet switched communication services. Although the packet switched networks may have location register functionality of their own, the GPRS typically utilises the HLRs and VLRs of the GSM system. Other systems, such as the proposed CDMA (Code Division Multiple Access) or UMTS (Universal Mobile Telecommunications System) are also provided with appropriate controller and location management functionalities.
One of the more recent proposals for the control of communications services is a combined or integrated network element providing control for both the packet switched communication service and the circuit switched communication service. More precisely, a UMSC (=UMTS MSC) node has been proposed, said UMSC comprising both the MSC and the SGSN functionalities. A UMSC node is intended for providing a combined location management for the mobile stations within its location arearouting area such that the location management may be provided for both the circuit and packet switched services by a single integrated element. The proposed integrated node or element may provide the location update procedure e.g. in a MAP (Mobile Application Part) protocol based network environment. Thus the UMSC can be defined as a logical entity that originates and terminates combined MAP (Mobile Application Part) operation. The UMSC is arranged to utilise the VLR of the MSC. An integrated UMSC node typically refers to a physical node that includes the MSC/VLR and SGSN logical entities. The signalling between these entities and/or other possible internal entities is arranged to occur within the integrated node. Thus the other network elements will see the integrated node as a single entity.
However, the inventor has found that if combined location management, such as the above referred integrated UMSC node, used the location cancellation cannot separate different communication services (e.g. the packet switched (PS) connection and the circuit switched (CS) connection) that may be provided simultaneously by means of the integrated node for the subscriber. This applies even if the circuit switched communication service and the packet switched communication service each have their own, from each other independent location update messages. The inventor has found that a problem arises especially in a situation where only one of the services (e.g. only the CS service or only the PS service) is to be relocated to a xe2x80x9cnewxe2x80x9d location/routing area and thus to a xe2x80x9cnewxe2x80x9d control node while the other remains in the xe2x80x9coldxe2x80x9d service area and should thus be controlled by the xe2x80x9coldxe2x80x9d node. More precisely, even though the old node receives the cancel location message, the old node does not know which one of the connections is to be relocated. A cancel location message may lead to deletion of all connections from the old integrated node or to other undesired situation in the system. The cancellation of all connections may occur, even though the situation may well be such that at least one of the connections should still be maintained in the old node despite the relocation of one or several other connections.
It is an aim of the embodiments of the present invention to address one or several of the above problems.
According to one aspect of the present invention, there is provided a method in a communications system providing communication services for a mobile station, the mobile station being arranged to use at least two different communication services provided by the communications system and the communications system comprising a first network element and a second network element for controlling the communication services provided for the mobile station, wherein the mobile station communicates by using at least two different communication services under the control of the first network element, comprising the subsequent steps of:
initiating relocation of the control of at least one of said communication services from the first network element to the second network element;
sending a message to the first network element, said message including information based on which it is possible to selectively relocate said at least one communication service to the second network element; and
selectively relocating said at least one communication service from the first network element to the second network element based on the information.
The first network element may be arranged to provide circuit switched communication services and packet switched communication services for the mobile station. The first network element may also provide combined location management for the at least two communication services before the relocation is initiated, and, after said at least one communication service is relocated, the first network element may provide location management for those communication services only that were not relocated.
According to another aspect of the present invention there is provided a communications system for providing communication services for a mobile station, the communications system providing the mobile station with at least two different communication services, the communications system comprising:
a first network element for controlling the at least two communication services provided for the mobile station for communication;
means for initiating relocation of the control of at least one of said communication services from the first network element to a second network element; and
means for sending a message to the first network element, said message including information based on which it is possible to selectively relocate said at least one communication service to the second network element, wherein the first network element is arranged to selectively cancel its control of the communication services based on the information.
According to another aspect of the present invention there is provided an integrated node in a communications system for providing a mobile station with at least two different communication services, comprising:
means for controlling a first communication service provided for the mobile station for communication;
means for controlling a second communication service provided for the mobile station for communication; and
means for processing a message from the communication system, said message including information based on which it is possible to selectively relocate one or several of the communication services to a second network element, wherein the integrated node is arranged to selectively cancel its control of the communication services to be relocated based on the information.
The embodiments of the invention provide several advantages. One of the benefits is that it may enable selective relocation of only one or some of the ongoing communication services handled by an integrated controller entity while the remaining connection or connections may continue and a disconnection of any communication services may be avoided.